The present invention relates generally to sensing the temperature of a rotating electromagnetic machine such as an electric motor or generator.
In many applications for rotating electromagnetic machines, the temperature of the machine must be monitored and managed. For instance, clothes washing machines are typically powered by an electric motor. Residential and commercial clothes washing machines are well known. A generally cylindrical drum or basket for holding the clothing and other articles to be washed is mounted within a cabinet and rotated by the electric motor. During a wash cycle, water and detergent or soap are forced through the clothes to wash them. The detergent is rinsed from the clothes, then during one or more spin cycles the water is extracted from the clothes by spinning the drum.
Vertical-axis washing machines have the drum situated to spin about a vertical axis. Articles to be washed are loaded into the drum through a door, which is usually situated on the top of the washing machine. A vertical-axis washing machine drum includes an agitator situated therein, which cleans clothes by pushing and pulling them down into the water. Horizontal-axis washing machines have the drum oriented to spin about an essentially horizontal axis. During wash cycles, the drum of the horizontal-axis washing machines rotates at a relatively low speed. The rotation speed of the drum is such that clothes are lifted up out of the water, using baffles distributed about the drum, then dropped back into the water as the drum revolves. In some washing machines, the rotation direction is periodically reversed to get the desired washing action.
Both vertical and horizontal-axis washing machines extract water from clothes by spinning the drum, such that centrifugal force extracts water from the clothes. It is desirable to spin the drum at a high speed and extract the maximum amount of water from the clothes in the shortest possible time. Spin time is reduced, but more power is required to spin at a higher speed.
When the washing machine drum contains a large load, the motor works harder to rotate the drum. Economically sized motors can get too hot if run continuously at high power, as may occur with a large load. Power use can be modulated to control temperature, if the temperature is known. Unfortunately, adding hardware for sensing the motor temperature adds cost and complexity to the system. A sensorless means for determining motor temperature is therefore desirable.
The present application addresses shortcomings associated with the prior art.